Preparation and application of green chitosan/ploy (vinyl alcohol) porous microspheres for the removal of hexavalent chromium

• CS/PVA porous microspheres were obtained by gelation and freeze-drying process. • Porous microspheres provided adsorption sites for removal of Cr(VI). • Porous microspheres containing 33 % PVA possessed the maximum adsorption capacity of 334.7 mg/g for Cr (Ⅵ). • The addition of 25–50% PVA ranged promoted smaller pore and more compact structure. • Adsorption kinetics fitted pseudo second order model. The chitosan/polyvinyl alcohol porous microspheres were obtained by first gelation and then freeze-drying process. The effects of polyvinyl alcohol (PVA) content on the structure of the porous microspheres and adsorption capacity for Cr(Ⅵ) were investigated. The microspheres were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectra (FTIR) and adsorption experiments. With the continuous increase of PVA content, the distribution of component materials and pore structure became more uniform with smaller pore. FTIR results showed that the strong interaction was formed between functional groups of PVA and those of chitosan, and porous microspheres provided adsorption sites of the amino and hydroxyl groups for the removal of Cr(VI). The porous microspheres containing 33 % PVA possessed the maximum adsorption capacity of 334.7 mg/g for Cr (Ⅵ) due to its most optimum balance between chitosan and PVA. Adsorption kinetics and equilibrium adsorption isotherms fitted pseudo second order model and Freundlich isotherm well, respectively.